Question

Complete combustion of a sample of a hydrocarbon on excess oxygen produces equimolar quantities of carbon dioxide and water. Which of the following could be the molecular formula of the compound?
A. C2H2
B.C2H6
C.C4H8
D.C6H6

Answer 1

C. C4H8 Given that the number of moles of CO2 and H2O produced from the combustion are equal, that means for every carbon atom, there are 2 hydrogen atoms because CO2 has only 1 carbon atom and H2O has 2 hydrogen atoms. So let's look at the available choices and see which one is correct. A. C2H2 This is a 1 to 1 ratio of carbon to hydrogen. Wrong answer. B. C2H6 This is a 1 to 3 ratio of carbon to hydrogen. Wrong answer. C. C4H8 This is a 1 to 2 ratio of carbon to hydrogen. Correct answer. D. C6H6 This is a 1 to 1 ratio of carbon to hydrogen. Wrong answer.